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Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F4/00—Monocomponent artificial filaments or the like of proteins; Manufacture thereof
  • D01F4/02—Monocomponent artificial filaments or the like of proteins; Manufacture thereof from fibroin
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D1/00—Treatment of filament-forming or like material
  • D01D1/02—Preparation of spinning solutions
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/02033—Core or cladding made from organic material, e.g. polymeric material

Definitions

• This invention provides for compositions and methods for drawing egel silk fibroin fibers.
• the resulting fibers can transmit light and hence can be used as optical fiber.
• the silk fiber of the invention can be used in materials such as textile, medical sutures, and tissue materials, as well as conferring optical properties into these materials.
• Optical fibers are typically flexible glass rods as thin as hair, which act as “wires” transmitting light or other data. In simple terms, they work by totally reflecting the light inside so that none of it leaks out.
• Synthetic polymer optical fibers are typically formed by extruding a viscous liquid through a small orifice called a spinneret. The viscous liquid is turned into a continuous filament which can be further solidified using post-extrusion processing.
• Fiber optics has made important contributions to the medical field, especially with regards to surgery. This has been accomplished by cutting and polishing the ends of a very slim bundle of fibers, to form a fiberscope. The light is sent to the site of inquiry, reflected off of the area that the doctor wishes to see, and sent back to a receiver. Afterwards, the image is magnified to be analyzed. Because optical fibers are so flexible, they are able to navigate around the curvy parts of the human body in areas such as the stomach, heart, blood vessels, and joints. It is now even becoming possible to do surgery with instruments attached to the optical fibers, such as joint surgeries. Fiber optics is becoming especially important in heart surgery, since it can be done without disturbing the functions of this delicate organ.
• a desirable alternative to glass or synthetic fibers would be a natural polymer fiber that is biodegradable, biocompatible, made by relatively simple techniques from renewable sources and aqueous procedures, can transmit light, and can also be weaved as conventional fibers into textiles, medical sutures, implantable tissue materials and in the mean time conferring optical properties to these materials.
• Silk electrogelation is a processing modality for silk fibroin protein.
• the egel process applies an electric field to solubilized silk fibroin solution, causing a transformation of the silk solution's random coil conformation into a meta-stable, silk I conformation.
• the resulting gel-like substance has many interesting properties, including muco-adhesive qualities and the ability to be further transformed into other conformations, including back to a random coil conformation or to an even higher-order ⁇ -sheet conformation.
• the silk fibers in accordance with the present invention may be manufactured without the need for high-temperature furnaces and the large expense of conventional systems.
• a silk fiber in accordance with the present invention uses a silk fibroin gel as a base material to create fibers with improved mechanical properties, such as, for example, shear strength.
• silk fibers in accordance with the present invention are biocompatible, biodegradable and implantable.
• the silk fiber produced with the method of the invention is transparent and can transmit light, and thus can be used as an optical fiber. Accordingly, the silk fibers may be used to monitor health conditions in vivo or may be implanted as a part of a sensing system to monitor and transmit information related to disease processes, treatment efficacy, and tissue growth.
• the silk fibroin gel in accordance with the present invention may be used as a coating for any number of optical fiber and transmission media devices.
• silk fibers of the invention can be incorporated in textile-based components or structures, such as mats, yarns, and braids, to provide the smart-structure or smart-material enhancement of carrying sensor or computational data through the structure, due to the light transmission properties of the silk fiber.
• One such application could be a soft robot body containing silk optical fiber, in which sensor data is transmitted through the body wall, without the need for traditional wiring.
• Silk optical fibers can be used as sensors, such as in the measurement of curvature in biomechanical applications (such as a spine) or in measuring structure and building deformation (such as bridges or buildings in normal or severe weather or under unusual loading, such as in an earthquake).
• the methods of producing silk egel fibers include an electrogelation process such as: applying an electric field (e.g., 25 VDC) to platinum electrodes submerged in solubilized silk solution. After a suitable time of electric field application (e.g., 10 minutes), a gel-like material has formed on the positive electrode, which has an increased level of meta-stable silk I conformation. When this silk gel is placed into a heated water bath, the gel dissociates into a fairly viscous liquid that settles at the bottom of the water bath. This viscous fluid can then be drawn out of the water bath to form a long fiber with unique mechanical properties and adjustable cross-section.
• an electric field e.g. 25 VDC
• the drawn fibers may be tougher if the dissociated gel is quenched in sub-zero temperature water (water which contains salt and crushed ice) before drawing into room-temperature air environment.
• sub-zero temperature water water which contains salt and crushed ice
• the behavior of the fibers in a humid environment is consistent with the elongation/contraction response that is reported in spider silks.
• the drawn egel fiber transmits light.
• Silk egel fiber drawing creates silk fibers with robust mechanical properties. Given the ability to artificially create fibers with customized properties and size provides for many applications. For example, all-silk composite materials can be constructed from silk fibroin solutions, eliminating the need for traditional spooled silk fibers.
• the drawn silk fibers exhibit supercontraction when fully hydrated. Furthermore, the fibers exhibit reversible stretching and contraction under humidity cycling. Accordingly, silk fibers may be useful as an analog to muscle fibers to make artificial muscles, actuators for small and/or biomimetic robots, or for other applications such as drug release.
• the drawn fibers transmit light
• the fiber can be used in vivo to monitor health conditions, implanted as part of a sensing system to monitor healing, or incorporated in tissue engineering constructs to relay information on tissue ingrowth and scaffold degradation.
• silk fibers can be used for long-range or short-range communication, in illumination, or laser-based applications. Because silk is biodegradable, the optical fiber would eventually degrade and absorb into the body.
• a method of creating a silk fiber comprising: applying an electric field to a solubilized silk fibroin solution to create a silk fibroin gel; quenching the silk fibroin gel in water to generate a viscous silk liquid; and drawing the silk fibroin gel from the viscous silk liquid to create a silk fiber.
• the water has a temperature at or below 0° C. In another embodiment, the water has a temperature in the range from 40° C. to 80° C., inclusive.
• the drawing of the silk is performed at a temperature within the range of 10° C. to 40° C., inclusive.
• the method further comprises drying the silk fiber.
• the method further comprises contracting the silk fiber.
• contracting the silk fiber includes reducing the ambient humidity to which the silk fiber is exposed.
• the method further comprises expanding the silk fiber.
• expanding the silk fiber includes increasing the ambient humidity to which the silk fiber is exposed.
• the silk fiber is processed with a methanol treatment to generate a water-insoluble silk fiber.
• the method further comprises wrapping a plurality of silk optical fibers.
• the silk fiber is an optical fiber.
• the method further comprises forming a fiber optic cable with the silk optical fiber.
• the method further comprises receiving, by the silk optical fiber, incident light from a light source.
• the silk optical fiber is a waveguide.
• the silk optical fiber is a single mode fiber. In another embodiment, the silk optical fiber is a multi-mode fiber.
• FIGS. 1A-1D show a series of photographs presenting a time lapse sequence showing effects of submerging electrogelated silk (egel) in 60° C.-75° C. water: ( 1 A) 5 seconds; ( 1 B) 15 second; ( 1 C) 25 seconds; and ( 1 D) 35seconds.
• FIG. 2 is a photograph showing formation of silk egel “structures” in 60° C.-75° C. water.
• FIGS. 3A-3D show a series of time lapse photographs showing fiber drawing of egel from a 60° C.-70° C. water bath.
• FIGS. 4A-4C show silk egel ( 4 A) before heating; ( 4 B) with heat gun; and ( 4 C) after heating to about 60° C.
• FIGS. 5A-5C show silk egel: ( 5 A) before heating; ( 5 B) in water bath to cool down; and ( 5 C) after extrusion from syringe.
• FIGS. 6A-6B show heated silk egel quenched in an ice bath: ( 6 A) after initial quenching; and ( 6 B) after about 1 minute.
• FIGS. 7A-7B depict a custom fixture for exploration of light carrying capability of drawn silk egel fiber: ( 7 A) overall setup; and ( 7 B) zoomed image of fiber holder.
• FIGS. 8A-8B presents images that demonstrate the ability for the drawn silk egel fibers to transmit light: ( 8 A) light projects from the end of the drawn silk egel fiber; and ( 8 B) bent fiber is glowing with light.
• FIGS. 9A-9C show images of ( 9 A) initial egel formation; ( 9 B) after 5 minutes of electrogelation; and ( 9 C) overview of power supply, egel tube setup, IR thermometer for recording temperature, and hot plate.
• FIGS. 10A-10C depicts egel silk fiber drawing from a ice water bath: ( 10 A) quenching of heated egel into an ice bath; ( 10 B) a egel silk fiber immediately after being drawn from the bath (using an insulated wire); and ( 10 C) a drawn egel silk fiber after some drying in air.
• FIG. 11 is a stereo microscope image of a typical egel silk fiber drawn from an ice water bath and dried in ambient air. The diameter between the bifurcations is approximately 100 ⁇ m.
• FIG. 12 shows time-lapse photographs of egel silk fibroin submerged in about 60° C. water. Over about a 5 minute period, the silk structure in the gel appears to separate from the water content, falling into a pool at the base of the beaker.
• FIGS. 13A-13E show egel silk fiber drawn from a heated bath: ( 13 A- 13 B) insulated wire dragging through silk pool; ( 13 C- 13 D) fiber drawn rapidly from the bath.
• FIGS. 14A-14E are time-lapse photographs of a weighted drawn silk egel fiber: ( 14 A) fiber at ambient humidity with 133 mg weight attached; and ( 14 B- 14 E) elongation of fiber after 20 seconds of exposure to steam.
• FIG. 15 shows an example humidity chamber showing the Kaz Ultrasonic Humidifier (right), Lufft humidity/temperature device (center), and drawn egel fiber hanging next to a metric scale (left).
• FIG. 16A-16C depicts drawn silk egel fiber exposed to dry humidity: ( 16 A) initial fiber length of about 15 cm with 33 mg weight attached at ambient humidity of 44.5%; ( 16 B) at 94.6% humidity; and ( 16 C) after evacuation to 47.8% humidity.
• FIGS. 17A-17B exhibits the change in drawn silk egel fiber length: ( 17 A) from 81.7% humidity to ( 17 B) 94.6% humidity.
• FIGS. 18A-18D represents a comparison of drawn egel silk fiber contraction at relative humidity levels: ( 18 A) 99.7%; ( 18 B) 86.3%; ( 18 C) 71.8%; and ( 18 D) 62.4%.
• FIG. 19 shows cardboard-mounted fibers positioned in Instron pneumatic grips for tensile tests.
• FIG. 20 is a graph showing a comparison of load-extension response between several drawn silk egel fibers.
• FIG. 21A-21B is a stereo microscope and images of three drawn egel fibers produced under unique conditions (1 mm scale bar).
• FIGS. 22A-22B shows scanning electron microscope (SEM) images of a drawn egel fiber: ( 22 A) at 1560 ⁇ ; and ( 22 B) 1960 ⁇ magnification.
• Synthetic polymer fibers are typically formed by extruding a viscous liquid through a small orifice called a spinneret.
• the viscous liquid is turned into a continuous filament which can be further solidified using post-extrusion processing.
• Four spinning methods are prevalent, including wet, dry, melt, and gel spinning.
• Wet spinning is used on materials that are dissolved in a solvent.
• the filaments are drawn through a spinneret that is submerged in a chemical bath that acts as a precipitating liquid. Dry spinning is also employed on materials in solution.
• solidification occurs as the solvent is driven off by gas (e.g., air)-driven evaporation.
• Melt spinning involves the extrusion of melted material through a spinneret and solidification by cooling.
• Optical fibers are transmission media that carry an optical signal from a light source to, for example, an optical receiver of that signal.
• Optical fibers and fiber optic cables may be used to transmit signals such as voice, video, and data signals.
• the data signal from a communication signal source such as a telephone or data modem is modulated onto a light wave and transported via the optical fibers to the optical receiver.
• the data signal is then recovered at the receiver using a demodulation process.
• Fiber optic cables and their optical fibers have inherent signal attenuation characteristics. Signals transmitted via an optical fiber are attenuated as they travel, and at some distance from the light source the signals reach a sufficiently low level as to require amplification.
• Conventional glass optical fibers are typically made by either a crucible method, where powdered silica is melted, or by a vapor deposition process.
• Crucible methods may be used to produce large diameter multimode fibers suitable for short-distance transmission of many light wave signals.
• Vapor deposition processes are used to create a solid cylinder of core and cladding material that is then heated and drawn into a thinner optical fibers for longer distance communication.
• Silk electrogelation is a processing modality for silk fibroin protein.
• the egel process applies an electric field (either direct or alternating current, referred to as DC or AC) to solubilized silk fibroin solution, causing a transformation of the silk protein's random coil conformation into a meta-stable, silk I conformation.
• the electric field can be applied through using a voltage source, such as a DC or AC voltage source.
• Direct current is produced by sources such as batteries, thermocouples, solar cells, etc.
• alternating current (AC) the general powder source for business and residence, may also be used to induce the electrogelation process, although the gel formation may not be as fast as the gelation process induced by direct current voltage.
• the resulting gel-like substance has a very sticky, thick, mucus-like consistency and has many interesting properties, including muco-adhesive qualities and the ability to be further transformed into other conformations, including back to a random coil conformation or to an even higher-order ⁇ -sheet conformation.
• the method of eletrogelation, the related parameters used in the eletrogelation process and the structural transition of silk fibroin during the electrogelation process may be found in WO/2010/036992, Active silk muco-adhesives, silk electrogelation process, and devices, which is incorporated herein as a reference in its entirety.
• silk fibroin includes silkworm fibroin and other insect or spider silk protein (Lucas et al., 13 Adv. Protein Chem. 107-242 (1958)).
• Silk fibroin can be obtained from a solution containing a dissolved silkworm silk or spider silk.
• the silkworm silk fibroins are obtained, for example, from the cocoon of Bombyx mori
• the spider silk fibroins are obtained, for example, from Nephila clavipes .
• the silk fibroins suitable for use in the present invention can be obtained from a solution containing a genetically engineered silk harvested from bacteria, yeast, mammalian cells, transgenic animals or transgenic plants. See, e.g., WO 97/08315 and U.S. Pat. No. 5,245, 012.
• An aqueous silk fibroin solution may be prepared from the silkworm cocoons using techniques known in the art. Suitable processes for preparing silk fibroin solution are disclosed in, for example, U.S. patent application Ser. No. 11/247,358, WO/2005/012606, and WO/2008/127401.
• the concentration of silk fibroin aqueous solution may by decreased by dilution, or increased by dialyzing a lower concentration silk fibroin solution against a hygroscopic polymer, for example, PEG, a polyethylene oxide, amylose or sericin. See, e.g., WO 2005/012606.
• the resulting silk solution may be further processed, e.g., through centrifugation or micro-filtration, to remove remaining particulates and to reach to a silk fibroin solution with minimal contaminants and reduced scattering for optical applications.
• the embodiments described herein provide for a silk egel fiber drawing process.
• the several Examples describe experiments conducted to provide alternative fabrication strategies for silk egel fiber drawing.
• the results of these experiments show the potential for creating fibers with a range of cross-sections and potentially impressive mechanical properties.
• the process is aqueous-based and easily set up and executed on a lab bench.
• the fibers generated can be long, and the process can be both continuous and automated. It appears that a wide range of diameters can be produced.
• the solubility of the dried fiber can be changed by a post-processing treatment to generate water-insoluble conformations.
• an alcohol treatment e.g., methanol treatment
• water annealing treatment of the silk fibers which can be included as part of a continuous processing approach, can provide water-insoluble silk fibers.
• the ability to drive the fiber diameters to very small cross sections could impart strength through the alignment of molecular chains along the fiber axis.
• an underwater spinneret may contribute to this strengthening effect.
• the use of the egel is key in generating fibers that rival the mechanical performance of native silkworm silk fiber.
• the silk conformation achieved with electrogelation may match the precursor gel-phase present in the glands of living silkworms and spiders before being extruded through spinnerets.
• This process of fiber drawing may mimic the native process, leading to superior outcomes to all other fiber formation processes using regenerated silk. See, e.g., Zhou et al., Silk Fibers Extruded Artificially from Aqueous Solutions of Regenerated Bombyx mori Silk Fibroin are Tougher than their Natural Counterparts, 21 Adv. Mats. 366-70 (2009). Indeed, the drawn egel silk fibers can be very strong—the smallest-diameter fibers made by the techniques taught herein show higher strength than cocoon fiber.
• the silk fiber made by the method of the present invention is quite transparent, can transmit light, such as a laser light, and therefore can be used as optical fiber.
• the embodiments of the present invention thus provide for a method of forming an silk fiber comprising applying an electric field to a solubilized silk fibroin solution, transforming the solubilized silk fibroin solution to a silk gel based upon the applied electric field, converting the silk fibroin gel to a viscous silk liquid (e.g., quenching the silk gel water to generate a viscous silk liquid), and drawing the silk liquid to form a silk fiber.
• the silk fibroin gel may be heated prior to the quenching step, and the silk fibroin gel may be heated to a temperature higher than the temperature of water used in the quenching step.
• the silk fibroin gel may be heated to about 60° C., and quenched in a cool water bath (temperature of the water bath is lower than 60° C., such as ⁇ 0° C.).
• the drawing may be done in water having a temperature at or below 0° C.; in the range from 40° C. to 80° C.; or within the range of 10° C. to 40° C.
• the method may further include drying the silk fiber.
• the dried silk fiber is quite transparent and exhibits transmission of laser light.
• the silk fiber may also be contracted, such as by reducing the ambient humidity to which the silk fiber is exposed; or expanded, such as by increasing the ambient humidity to which the silk fiber is exposed. Additionally, the silk fiber may be further processed, for example with a methanol treatment, to generate water-insoluble silk fiber.
• the silk fiber is used as optical fiber.
• the method may also further include forming a fiber optic cable with a silk optical fiber or a plurality of silk optical fibers.
• the silk optical fiber of the present invention may receive incident light from a light source; and may act as a waveguide, a multimode fiber, or a single mode fiber.
• a plurality of silk optical fibers may be wrapped into a fiber optic cable by techniques well-known in the art.
• Silk fibers produced from the method of the invention may be wrapped with other type of fibers made from silk or other materials, natural or synthetic, into a fiber bundle or fiber composite.
• a fiber composite may be made from one or more silk fibers of the invention combined with one or more native silkworm fibroin fibers to form a silk-fiber-based matrix.
• Immunogenic components in the silk (such as sericin) may be removed from native silk fiber if such silk fiber based matrix is to be used as implantable materials.
• These silk fiber based matrix may be used to produce tissue materials for surgical implantation into a compatible recipient, e.g., for replacement or repair of damaged tissue.
• tissue materials that can be produced include ligaments or tendons such as anterior cruciate ligament, posterior cruciate ligament, rotator cuff tendons, medial collateral ligament of the elbow and knee, flexor tendons of the hand, lateral ligaments of the ankle and tendons and ligaments of the jaw or temporomandibular joint; cartilage (both articular and meniscal), bone, muscle, skin and blood vessels.
• ligaments or tendons such as anterior cruciate ligament, posterior cruciate ligament, rotator cuff tendons, medial collateral ligament of the elbow and knee, flexor tendons of the hand, lateral ligaments of the ankle and tendons and ligaments of the jaw or temporomandibular joint
• cartilage both articular and meniscal
• Methods of making tissue materials or medical device using silk-fiber based matrix or silk composite containing silk fibers may be found in, e.g., U.S. Pat. No. 6,902,932, Helically organized silk fibroin fiber bundles for matrices in
• Silk fibers produced from the method of the invention may be incorporated into textile (e.g., yarns, fabrics) and textile-based structures using traditional textile-processing equipment, including winding, twisting, flat braiding,weaving, spreading, crocheting, bonding, tubular braiding, knitting, knotting, and felting (i.e., matting, condensing or pressing) machines.
• textiles e.g., yarns, fabrics
• textile-based structures using traditional textile-processing equipment, including winding, twisting, flat braiding,weaving, spreading, crocheting, bonding, tubular braiding, knitting, knotting, and felting (i.e., matting, condensing or pressing) machines.
• Such textiles can be incorporated in composite materials and structures through many known composite-manufacturing processes.
• Silk fibers produced from the method of the invention may be combined with other forms of silk material, such as silk films (WO2007/016524), coatings (WO2005/000483; WO2005/123114), microspheres (PCT/US2007/020789), layers, hydrogel (WO2005/012606; PCT/US08/65076), mats, meshes, sponges (WO2004/062697), 3-D solid blocks (WO2003/056297), etc., to form an all-silk composite.
• the silk composite material can be reinforced by silk fiber, as well as incorporate the optical property of silk optical fiber into the composite.
• a one, two or three-dimensional silk composite may be prepared by exposing silk fiber with silk fibroin solution and drying or solidifying the silk fibroin solution containing the silk fiber of the invention to form the silk composite.
• Different solidifying processes and additional approaches for processing silk fibroin solution into different formats of silk materials can be used. See, e.g., WO/2005/012606; WO/2008/150861; WO/2006/042287; WO/2007/016524; WO 03/004254, WO 03/022319; WO 04/000915.
• silk fiber produced by the method of the invention can be combined with one or more other natural or synthetic biocompatible or non-biocompatible polymers, and incorporated into a composite with different material formats, such as fibers, films, coatings, layers, gels, mats, meshes, hydrogel, sponges, 3-D scaffold, and the like.
• the non-limiting biocompatible polymers include polyethylene oxide, polyethylene glycol, collagens (native, reprocessed or genetically engineered versions), polysaccharides (native, reprocessed or genetically engineered versions, e.g.
• hyaluronic acid alginates, xanthans, pectin, chitosan, chitin, and the like
• elastin native, reprocessed or genetically engineered and chemical versions
• agarose polyhydroxyalkanoates
• pullan starch (amylose amylopectin)
• cellulose cotton, gelatin, fibronectin, keratin, polyaspartic acid, polylysin, alginate, chitosan, chitin, poly lactide, poly glycolic, poly(lactide-co-glycolide), poly caproloactone, polyamides, polyanhydrides, polyaminoacids, polyortho esters, poly acetals, proteins, degradable polyurethanes, polysaccharides, polycyanoacrylates, glycosamino glycans (e.g., chrondroitin sulfate, heparin, etc.), and the like.
• non-biodegradable polymers include polyamide, polyester, polystyrene, polypropylene, polyacrylate, polyvinyl, polycarbonate, polytetrafluorethylene and nitrocellulose material.
• silk fiber When incorporating silk fiber into the composite, one or more of these aforementioned polymers can be combined. See also, e.g., U.S. Pat. No. 6,902,932; U.S. Patent Application Publication Nos. 2004/0224406; 2005/0089552; 2010/0209405.
• composite materials containing the silk fiber of the invention can be tailored to specific applications.
• single fiber layers have been shown to be very tough and flexible.
• Cylindrical mandrels can be used to produce very stiff rod or tubular constructs that can have impressive compressive, tensile, flexural, and torsional properties. Custom wavy or highly curved geometries can also be produced.
• the composite material generally enhances the matrix properties such as mechanical strength, porosity, degradability, and the like, and also enhances cell seeding, proliferation, differentiation or tissue development when used as medical suture or implantable tissue materials.
• Silk fibroin in the silk fiber can also be chemically modified with active agents in the solution, for example through diazonium or carbodiimide coupling reactions, avidin-biodin interaction, or gene modification and the like, to alter the physical properties and functionalities of the silk protein. See, e.g., PCT/US09/64673; PCT/US10/42502; PCT/US2010/41615; U.S. patent application Ser. No. 12/192,588.
• Silk fiber of the invention may include at least one active agent.
• the agent may be embedded in the fiber or immobilized on the surface of the fiber.
• the active agent may be a therapeutic agent or biological material, such as chemicals, cells (including stem cells) or tissues, proteins, peptides, nucleic acids (e.g., DNA, RNA, siRNA), nucleic acid analogues, nucleotides, oligonucleotides or sequences, peptide nucleic acids(PNA), aptamers, antibodies or fragments or portions thereof (e.g., paratopes or complementarity-determining regions), antigens or epitopes, hormones, hormone antagonists, cell attachment mediators (such as RGD), growth factors or recombinant growth factors and fragments and variants thereof, cytokines, enzymes, antioxidants, antibiotics or antimicrobial compounds, anti-inflammation agents, antifungals, viruses, antivirals, toxins, prodrugs, drugs, dyes, amino acids, vitamins, chem
• antibiotics suitable for use herein include, but are not limited to, aminoglycosides (e.g., neomycin), ansamycins, carbacephem, carbapenems, cephalosporins (e.g., cefazolin, cefaclor, cefditoren, cefditoren, ceftobiprole), glycopeptides (e.g., vancomycin), macrolides (e.g., erythromycin, azithromycin), monobactams, penicillins (e.g., amoxicillin, ampicillin, cloxacillin, dicloxacillin, flucloxacillin), polypeptides (e.g., bacitracin, polymyxin B), quinolones (e.g., ciprofloxacin, enoxacin, gatifloxacin, ofloxacin, etc.), sulfonamides (e.g., sulfasal
• Exemplary cells suitable for use herein may include, but are not limited to, progenitor cells or stem cells (e.g., bone marrow stromal cells), ligament cells, smooth muscle cells, skeletal muscle cells, cardiac muscle cells, epithelial cells, endothelial cells, urothelial cells, fibroblasts, myoblasts, chondrocytes, chondroblasts, osteoblasts, osteoclasts, keratinocytes, hepatocytes, bile duct cells, pancreatic islet cells, thyroid, parathyroid, adrenal, hypothalamic, pituitary, ovarian, testicular, salivary gland cells, adipocytes, and precursor cells.
• progenitor cells or stem cells e.g., bone marrow stromal cells
• ligament cells smooth muscle cells
• skeletal muscle cells skeletal muscle cells
• cardiac muscle cells epithelial cells
• endothelial cells urothelial cells
• fibroblasts myoblasts
• Exemplary antibodies include, but are not limited to, abciximab, adalimumab, alemtuzumab, basiliximab, bevacizumab, cetuximab, certolizumab pegol, daclizumab, eculizumab, efalizumab, gemtuzumab, ibritumomab tiuxetan, infliximab, muromonab-CD3, natalizumab, ofatumumab omalizumab, palivizumab, panitumumab, ranibizumab, rituximab, tositumomab, trastuzumab, altumomab pentetate, arcitumomab, atlizumab, bectumomab, belimumab, besilesomab, biciromab, canakinumab, capromab pende
• Exemplary enzymes suitable for use herein include, but are not limited to, peroxidase, lipase, amylose, organophosphate dehydrogenase, ligases, restriction endonucleases, ribonucleases, DNA polymerases, glucose oxidase, laccase, and the like.
• Additional active agents to be used herein include cell growth media, such as Dulbecco's Modified Eagle Medium, fetal bovine serum, non-essential amino acids and antibiotics; growth and morphogenic factors such as fibroblast growth factor, transforming growth factors, vascular endothelial growth factor, epidermal growth factor, platelet derived growth factor, insulin-like growth factors), bone morphogenetic growth factors, bone morphogenetic-like proteins, transforming growth factors, nerve growth factors, and related proteins (growth factors are known in the art, see, e.g., Rosen & Thies, C ELLULAR & M OLECULAR B ASIS B ONE F ORMATION & R EPAIR (R.G.
• cell growth media such as Dulbecco's Modified Eagle Medium, fetal bovine serum, non-essential amino acids and antibiotics
• growth and morphogenic factors such as fibroblast growth factor, transforming growth factors, vascular endothelial growth factor, epidermal growth factor, platelet derived growth factor
• anti-angiogenic proteins such as endostatin, and other naturally derived or genetically engineered proteins
• polysaccharides, glycoproteins, or lipoproteins such as antibiotics and antiviral agents, chemotherapeutic agents (i.e., anticancer agents), anti-rejection agents, analgesics and analgesic combinations, anti-inflammatory agents, and steroids.
• the active agent may also be an organism such as a bacterium, fungus, plant or animal, or a virus.
• the active agent may include neurotransmitters, hormones, intracellular signal transduction agents, pharmaceutically active agents, toxic agents, agricultural chemicals, chemical toxins, biological toxins, microbes, and animal cells such as neurons, liver cells, and immune system cells.
• the active agents may also include therapeutic compounds, such as pharmacological materials, vitamins, sedatives, hypnotics, prostaglandins and radiopharmaceuticals.
• Additional applications for silk optical fibers drawn from silk egels include photomechanical actuation, electro-optic fibers, and smart materials.
• the silk fibers of the present invention When the silk fibers of the present invention is used in the textile, medical suture materials or tissue materials, either separately or combined into a composite, stimulus can be incorporated in the aforementioned method of producing the textile medical suture materials or tissue materials.
• chemical stimuli, mechanical stimuli, electrical stimuli, or electromagnetic stimuli can also be incorporated herein.
• the silk fiber contained in the textile, medical suture materials or tissue materials can be used to transmit the optical signals that may be from the stimuli or converted from the stimuli originated from the environment (e.g., tissue, organ or cells when used as implant materials) and influence the properties of the textile, suture or tissue materials.
• silk optical fiber may be used to transmit the optical signal to the applied medium, such as cells or tissues when used as implant materials, and modulate the activities of the cells or tissues.
• cell differentiation is known to be influenced by chemical stimuli from the environment, often produced by surrounding cells, such as secreted growth or differentiation factors, cell-cell contact, chemical gradients, and specific pH levels, to name a few. Some stimuli are experienced by more specialized types of tissues (e.g., the electrical stimulation of cardiac muscle). The application of such stimuli that may be directly or indirectly transmitted by optical signal is expected to facilitate cell differentiations.
• a controlled drug delivery system may be made available by incorporating the silk optical fiber into the system, for example, the drug administration and release can be controlled in a manner that precisely matches physiological needs through the external stimuli applied on the silk optical fiber.
• the critical angle at which a light ray can enter the first medium and then travel between the two mediums, without crossing into the second medium. If the angle at which the ray passes through the first medium is greater than the critical angle, the ray will experience total internal reflection, where it will just reflect off the surface between the two mediums and reenter the first medium. This is the case with contemporary optical fibers.
• the silk optical fiber of the present embodiments is well-able to conduct light while bent, as shown in FIG. 8 b .
• the silk-based optical fibers of the present invention may be used, for example, in systems for endoscopy which combine fiber optics and powerful lenses.
• the medical device may include objective lenses, rod lenses, ocular lenses, light fibers, light source, camera for imaging.
• a micro-camera may be attached to the eyepiece and an image viewed on a monitor.
• the endoscopy system may use charge-coupled devices that capture and store image data. For example, a 2D array of individual elements that can store an electric charge, and can respond to 70% of the incident light.
• Light sourced include tungsten filament lamp, halogen reflector lamp, rare-earth xenon lamp give high intensity light and true color display (xenon daylight effect).
• the typical flexible endoscope has a bending radius of about 15 mm and two silk fiber optic cables: one is a light conduit (incoherent), second is used to image transmission (coherent).
• the image fiber may have an image resolution of approximately 10,000 pixels per square mm.
• Applications for endoscopy include surgical imaging systems that can simulate the optimal path for the surgeon (e.g., inside the brain for neurosurgery). In laser, brain surgery within the skull, the endoscopic device is threaded like a wire through a one-eighth-inch incision in the skull, implanted in the tumor like a biopsy needle, and turned on for spurts of a few seconds.
• nonimaging edge-ray concentrators may be well suited to a number of laser fiber optic contact surgical procedures where sizable increases in irradiance are required at maximum collection efficiency, and light must be emitted uniformly over a wide angular range.
• the delivered irradiance from nonimaging designs can be more than double, at maximum radiative efficiency, while producing a Lambertian absorber, i.e., uniform emission over the entire hemisphere.
• Additional modifications of the egel drawing process are supported by the disclosure provided herein, including automation, that may improve the generation of controllable and consistent fiber diameters, and may eliminate the bifurcation anomalies. Further optimizing and characterizing silk egel drawing, improving the quality control of the fibers, generating improved light-carrying fibers, and exploring further the hydration-driven contraction and elongation are within the scope of the present invention.
• the present invention may be as defined in any one of the following numbered paragraphs:
• Solubilized silk fibroin aqueous stock solutions were prepared as described previously. Sofia et al., 54 J. Biomed. Mater. Res. A 139-48 (2001). Briefly, cocoons of B. mori were boiled for 20 min in an aqueous solution of 0.02 M sodium carbonate, and then rinsed thoroughly with water (ultra-pure water processed via Milli-Q® Water System, Millipore, Billerica, Mass.). After drying, the extracted silk fibroin was dissolved in a 9.3 M LiBr solution at 60° C. for 4 hr, yielding a 20% (w/v) solubilized silk fibroin solution.
• the resulting solution was dialyzed against distilled water using Slide-A-Lyzer® 3.5K MWCO dialysis cassettes (Pierce, Rockford, Ill.) for three days to remove the residual salt.
• the solution was optically clear after dialysis and was centrifuged twice at 10,000 rpm for 20 min to remove silk aggregates as well as debris from original cocoons.
• the final concentration of solubilized silk fibroin aqueous solution was approximately 8% (w/v). This concentration was determined by drying the solution with a known volume and weighing the residual solid. The 8% silk fibroin solution was stored at 4° C. and diluted with water before use.
• the autoclaved silk solution After a week of storage at 5° C.-10° C., the autoclaved silk solution exhibited some electrogelation response, albeit reduced. As subsequent experiments appeared to suggest, the electrogelation of a heated silk solution may have changed the conformation of the silk solution from random coil to silk I, but that the material was not staying in contact with the positive (typically platinum) electrode.
• Electrogelated silk was first created in a “standard” setup (8% w/v silk solution, platinum electrodes, and Falcon tube as above). After 10 min of electrogelation, the gel which formed on the positive electrode was transferred to a beaker containing water heated to 60° C.-75° C.
• FIG. 1 shows images of the gel response at 10 sec time intervals. Upon immersion in the warm water, the egel on the Pt seemed to dissociate and fall to the base of the beaker, apparently due a density differential. Simultaneously, any bubbles trapped in the egel rose to the water surface as they were released. The dissociation process continued until it appeared only ⁇ -sheet material was remaining on the Pt electrode.
• FIG. 3 shows time lapse photos of a “fiber” being drawn out of the heated bath. The fiber was drawn up at a rate of about 1 inch/second. Initial success led to fiber lengths of between 40 and 50 inches. The fiber lengths could be longer, depending on the amount of silk in the water, the temperature of the water, and the drawing rate.
• the drawn fibers were very sticky (if two fibers tangled, they would stick together). Over a period of minutes, the fiber would become thinner, less sticky, and more brittle. After between 40 min and 60 min, the fibers could be handled without becoming stuck to other surfaces or itself. Perhaps the solidification is due to a drying effect, where water entrained in the fiber was evaporating. After drying, the fibers had surprising strength, but would quickly become soft when rehydrated in water (especially warm water).
• thermocouple was used to monitor temperature of the egel and liquid throughout the experiment with National Instruments' CompactDAQ data acquisition hardware and LabVIEW software. This experiment was conducted by performing two complete heating/cooling cycles. A heat gun was used for heating and a water bath for cooling ( FIG. 5 b ).
• this experiment included the use of a type T thermocouple and National Instruments' CompactDAQ data acquisition hardware and LabVIEW software to monitor bath temperature.
• Silk egel was placed into a beaker of water heated to 60° C. After the egel would dissociate and sink to the bottom of the water bath, “fibers” of the liquid silk were drawn upward out of the bath. Depending on speed and height above the water bath, the fibers could be drawn to various diameters. After hanging each drawing fiber on a lab bench shelf, the initially sticky and non-uniform fiber would begin to dry/solidify. The fiber also tended to decrease in diameter and become more uniform. The final fibers exhibited impressive tensile properties, but were fairly brittle. If the dry fibers were wrapped into a curvature of less than about 90° C., they tended to fracture. Although the surface of the fiber was more smooth than after initial drawing, there were still noticeable bumps and rough sections on the fiber.
• an ice bath was created using a beaker of tap water and ice chips. The temperature was measured to be around 0° C.
• silk egel was first heated to above 60° C. with a heat gun set to medium. The egel was extruded through the needle end of the syringe (no needle attached) into the ice bath.
• the gel formed a vertical “fiber” that tended to stay suspended in the water, as shown in FIG. 6 a .
• the appearance of the gel tended to change from fairly transparent to a whitish color, as shown in FIG. 6 b . This was speculated to be due to conversion of the silk I egel conformation to ⁇ -sheet. Future materials characterization will confirm this.
• the liquid silk “fiber” that had been quenched in the ice bath was then drawn out of the bath.
• the fiber could be drawn to a fairly long length.
• the fiber was as sticky as the prior fibers, but more prone to failure during drawing. This fiber appeared to be much more homogeneous, with a fairly smooth surface and consistent cross-sectional geometry.
• the fiber was found to have become smaller in diameter, but overall was much tougher than the prior fibers: It was not as brittle and could withstand considerable tensile loading. The fiber appeared to be fairly transparent, which provides promise that such fibers could be used to transmit light.
• Drawn silk egel fibers appear to be fairly transparent, and may be manufactured and used to transmit light.
• a simple experimental apparatus was built, as shown in FIG. 7 a in which a manual x-y stage was mounted vertically to an aluminum base. A presentation-style laser pointer was held firmly to the stage. A fiber holder was formed using machinable wax. A very small hole was drilled in the wax to snugly hold an egel fiber, as shown in FIG. 7 b .
• the results of the tests, shown in FIG. 8 a laser light was carried through a fiber and projected onto a surface from the fiber end. The figure shows a second light patch above the fiber, which represents the direct transmission of light through the fiber holder hole.
• FIG. 8 b demonstrates the ability of a fiber to transmit light around a bend. Adjustments assured that the images are not due to light reflection on the outside of the fibers.
• Silk egel fibers were drawn from an ice bath after undergoing one heating (60° C.) and quenching ( ⁇ 0° C.) cycle.
• FIG. 9 shows egel being formed on 3 platinum electrodes in a shortened Falcon tube. As shown, only one negative electrode is necessary.
• the silk egel was placed in a 10 ml plastic syringe and heated to above 60° C. with a heat gun set to medium. The egel was extruded through the needle end of the syringe (no needle attached) into an ice bath, as shown in FIG. 10 a . As before, the egel material would tend to form a vertical underwater “fiber” that would stay suspended in the water.
• FIG. 10 b shows a fiber immediately after being drawn.
• FIG. 10 c shows a fiber tensioned between two insulated wires after about 30 min of air drying. Note that the beads that appear initially on the drawn fiber tend to dissipate with drying. Pulling on the fiber shows the fiber to be impressively strong for its diameter. In addition, the fibers drawn from the ice bath are quite tough after drying.
• FIG. 11 shows a stereo microscope image of one of the silk egel fibers that was drawn from the ice water bath. The bifurcations are likely water beads ( FIG. 10 b ) that have dried. In the straight segments between the bifurcations, the fiber diameter is approximately 100 ⁇ m. The fiber is noticeably transparent when viewed under a microscope.
• FIG. 9 c A Fisher Scientific hot plate ( FIG. 9 c ) was used to heat milli-Q water to about 60° C.
• Egel was formed using three platinum electrodes, as shown in FIGS. 9 a and 9 b .
• the platinum electrodes with the egel attached were submerged in the heated water bath, as shown in FIG. 12 , seemingly causing the silk from the egel to separate from the gel's water content.
• FIGS. 12 c and 12 d are studied closely, the silk material can be seen falling into a pool at the base of the beaker. Over a span of 5 min, most of the egel is removed from the electrodes.
• a 93.31 mm-long dried fiber was suspended in an empty 4 L beaker, with a 133 mg weight attached, as shown in FIG. 14 a .
• Boiling water was poured into the beaker and the fiber length was monitored with a camera ( FIGS. 14 b - e ).
• Significant elongation was seen after the fiber was exposed to the hot steam for about 20 sec. The total elongation exceeded approximately 35% of the original fiber length. After removal of humidity generated by the steam, the fiber contracted almost completely to its original length of about 93 mm.
• a custom-designed and-built humidity chamber was fabricated for studying small-contraction cycling. Using 1 ⁇ 8′′ acrylic, a 24 ⁇ 24 ⁇ 24 in3 chamber was fashioned.
• a Kaz Model V5100NS Ultrasonic Humidifier shown in FIG. 15 , was positioned inside the chamber, with a capability of bringing the internal humidity from room ambient relative humidity (around 44%) to about 95%. Because the humidifier uses ultrasonic energy to create a humid mist, the chamber temperature does not change appreciably from ambient temperature (around 26° C. on this day of testing).
• a Lufft C200 hand-held humidity/temperature measurement device was used to monitor chamber conditions.
• a drawn egel fiber (a quenched fiber) was suspended from the top of the chamber, with a 33 mg weight attached to the end with laboratory-grade tape.
• the initial fiber length was about 15 cm, as seen in FIG. 16 a .
• the ultrasonic humidifier was turned on. In a span of about 2 min, the relative humidity inside the chamber increased from ambient humidity (around 44%) to about 95%.
• FIG. 16 b horizontal lines added for clarity
• the humidity increased to about 95%
• the drawn egel fiber elongated approximately 1.2 cm, which is about an 8% increase from the original length.
• results showed that the egel fibers were all significantly stiffer than the cocoon fiber.
• the fibers that had undergone humidity cycles with an ultrasonic humidifier exhibited unique load-extension response from the other two drawn egel samples: while all egel fibers exhibited an initially steep linear elastic response, the cycled fibers exhibited significant plastic strain after a peak load was reached.
• the virgin silk egel fiber and fiber that was cycled with hot steam both failed catastrophically after their peak load was reached.
• Table 2 shows the diameter and peak tensile stress for each fiber tested. In general, the smaller the fiber, the greater the tensile strength. This is consistent with published results from both cocoon silk and regenerated silk fibroin fibers and is likely due to heightened alignment that occurs with the draw-down of the fiber diameter.
• the drawn egel fiber that had undergone humidity cycling with heated steam was, by far, the strongest. It exhibited much higher strength than cocoon fiber.
• FIG. 21 b shows images of three drawn egel fibers: a fiber that had undergone humidity cycles with an ultrasonic humidifier; a virgin drawn egel fiber; and a fiber that had undergone quenching in an ice bath before drawing. Given all fibers have been drawn by hand, the fiber diameters vary and there are bifurcations, or bulges, that can be retained by the fiber. All of the fibers appear to be transparent, thus light can be transmitted through them.

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• 2010
  • 2010-09-28 CA CA2775706A patent/CA2775706A1/en not_active Abandoned
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• 2012
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